Scanning near-field optical microscopy (SNOM) is an ideal experimental measuring system in nano-optical measurements and characterizations. Besides microscopy with resolution beyond the diffraction limit, spectroscope with nanometer resolution and other instruments with novel performances have been indispensable for researches in nano-optics and nanophotonics. This paper reviews the developing history of near-field optical (NFO) measuring method and foresees its prospects in future. The development of NFO measurements has gone through four stages, including optical imaging with super resolution, near-field spectroscopy, measurements of nanooptical parameters, and detections of near-field interactions. For every stage, research objectives, technological properties and application fields are discussed.